面试题与答案

Abstraction involves hiding the unnecessary details while encapsulation involves bundling the data and methods that operate on the data into a single unit.

Abstract classes are classes that cannot be instantiated and may contain abstract methods. Subclasses must implement these abstract methods.

Example:

abstract class Shape {
  abstract calculateArea();
}

Composition involves combining objects to create more complex ones, while inheritance involves creating a new class by inheriting properties and behaviors from an existing class.

Multiple inheritance allows a class to inherit properties and behaviors from more than one superclass. Some languages support it directly, while others provide alternatives like interfaces.

In C++, a friend class is a class that is not a part of the class hierarchy but is granted access to the private and protected members of another class.

SOLID is an acronym for five design principles in OOP: Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion. These principles aim to make software designs more understandable, flexible, and maintainable.

The diamond problem occurs when a class inherits from two classes that have a common ancestor. It can lead to ambiguity in the inheritance hierarchy, especially if the common ancestor has members.

Covariant return type allows a method in a subclass to return a more derived type than the method in the base class. It is a feature supported by some programming languages, including C++ and Java.